Optical encoders are useful for recording a movement of an object, so that the same movement of the object, or of another similar object, can later be repeated in a controlled manner. As an example, manufacturing apparatus can be controlled to robotically repeat a series of motions. The motions can be part of a process for robotically working on a device being manufactured, such as an automobile. In order to enable such repetition, an initial mechanical movement of the manufacturing apparatus can be translated into a light signal and can then be encoded as an electronic signal by detection of the light signal. A code wheel mechanically coupled with a robotic arm of the manufacturing apparatus can rotate around an axis together with rotation of the robotic arm. The code wheel can have a ring of alternating light reflective and non-reflective bands arranged around the axis. A focused light source such as a light emitting diode (“LED”) can be directed from a fixed position onto the ring. As the code wheel rotates on the axis, induced by movement of the robotic arm, light beam pulses are reflected from the light reflective bands, as light from the fixed LED successively strikes them. These reflected light beam pulses constitute a light signal encoding the rotary motion of the code wheel. The light signal can then be converted into an electrical signal. A photodetector can receive the reflected light beam pulses and encode the light signal. The electrical signal can be digitally recorded for later access and then utilized to implement controlled repetition of the movement of a robotic arm.
Although a variety of optical encoders have been developed, there is a continuing need for improved optical encoders offering greater efficiency and capability to record motions.